Penclomedine (NSC-338720; 3,5-dichloro-2,4dimethoxy-trichloromethylpyridine) is a synthetic alpha-picoline derivative and was first identified by the National Cancer Institute as a potential antitumor agent in the P388 Leukemia prescreen. It was selected for preclinical development by the NCI after demonstrating activity against two in vivo breast tumor models, human MX-1 mammary adenocarcinoma and murine CD8F1 adenocarcinoma. The mechanism of action is undetermined although cross-sensitivity studies suggest it may act as an alkylating agent. This is a phase I study using the drug penclomedine in patients for whom no effective anticancer therapy exists. As part of this study an oral bioavailability study will be conducted. Penclomedine will be given as an oral dose each day for five consecutive days, repeating the cycle every four weeks. Study endpoints are: determination of the maximum tolerated dose (MTD) and phase II dose of penclomedine; description and quantitation of toxicities of penclomedine; and description of the pharmacokinetic behavior of penclomedine.